The present invention relates to a fiber-treatment composition which is based on a microemulsion of carboxyl-modified organopolysiloxane, and more specifically relates to a fiber-treatment composition which is based on a microemulsion, said microemulsion having an average particle size not larger than 0.15 micrometers, of a carboxyl-modified organopolysiloxane which has a degree of polymerization of 350 to 2,000 and which contains at least two carboxyl groups in each molecule.
Emulsions having an average particle size of at least 0.3 micrometers, and prepared by the emulsification of carboxyl-modified organopolysiloxane in the presence of at least one type of anionic or nonionic surfactant using an emulsifying device such as, for example, an homogenizer, colloid mill, line mixer or propeller mixer, are used in the art in order to impart softness, smoothness, wrinkle resistance, elongation recovery, water repellency, etc., to fibrous materials of, for example, natural fiber such as cotton, flax, silk, wool, angora or mohair; regenerated fiber such as rayon or bemberg; semisynthetic fiber such as acetate; synthetic fiber such as polyester, polyamide, polyacrylonitrile, polyvinyl chloride, vinylon, polyethylene, polypropylene, spandex; or inorganic fiber such as glass fiber, carbon fiber or silicon carbide fiber. Refer to Japanese patent application laid open (Kokai) No. 55-152864 (152,864/80).
However, the aforesaid carboxyl-modified organopolysiloxane emulsions having average particle sizes of at least 0.3 micrometers suffer from a number of serious problems. Their stability during the agitation, circulation, and expression of the treatment bath which are necessarily encountered during fiber treatment (mechanical stability); their stability when diluted (dilution stability, for example, 20-fold to 100-fold dilution with water); and their stability when used with various additives (blending stability) are all unsatisfactory. These emulsions undergo de-emulsification as a consequence, and the organopolysiloxane floats up on the treatment bath and in this state will stain the fibrous material as oil droplets (oil spots).